In general, people with darker skin tones (i.e. with more melanin) are less likely to suffer from UV-induced skin cancers.
It has been traditionally believed that skin pigmentation is the most important photoprotective factor, since melanin, besides functioning as a broadband UV absorbent, has antioxidant and radical scavenging properties.
However, there is growing evidence that the relationship between pigmentation and photoprotection is far more complex than assumed.
Although it is known that melanin can very effectively protect against DNA damage from short-wavelength (UV) light, no scientific studies have so far pinpointed the exact mechanisms involved.
See: The Protective Role of Melanin Against UV Damage in Human Skin in Photochemistry and Photobiology, Volume 84, (3): 539–549.